egr valve..????

[bucket]

does it open under vacum or close..
and...
what good does it do??

 

[gmjunkie]

does it open under vacum or close..
and...
what good does it do??

It is activated by vacuum,but not until the ECM tells it to!! There is a vacuum solenoid that is controlled electronically by the ECM!! It recirculates unburned exhaust gases,it's part of the emissions controls!!

 

[TedC]

Reduces combustion temps. I'll get ping on my 1989 if it is not working correctly.

 

[G Winter]

Reduces combustion temps. I'll get ping on my 1989 if it is not working correctly.

Yes very true most of the time. EGR is a good thing as long as it works right. Does NOT effect power.

Glenn

 

[bucket]

it just seems to me that anything other than fuel/air mix would be counter productive to performance..
so i got a second opinion..(no offence)
it's ok to leave in on there because it's tied to electronic sensors and gizmos( thats the technikal term)
if you dont live in california...you can make a solid gaskit out of ..let say..a beer can( if you can find one)...this will effectivly refuse the unwanted exhaust from intering into the sanctity of the inner plenium...
also with out effecting the electronik gizmos....
in the other world..( the unseen world of the outlaw street guy).
1/4" pipe plugs (available at all hardware stores)will screw directly into where the recirculation pipeing plumbing devices were screwed into in the first place ....i'm jus sayin...under no circumstances should you disconnect and or render usless the useless smog / horsepower robing devices on yer fine ride.
if G.M. would have wanted you to have a pure motor they would have had you born earlier..
so leave it stock...because..after all
stock is better...
right?

 

[TedC]

bucket, I understand your view, but let me add what I learned about EGRs on L98s. EGRs are now integrated into the design of our engines. Let's say you prevent the EGR from working using a solid gasket. On a L98, the ECM monitors the EGR temp switch, which will post an error code when the ECM senses that EGR exhaust is not flowing. This may sound strange, but preventing the EGR from working has a negative on normal driving performance. This comment does not apply to WOT. Under WOT the EGR is not engaged, and as G Winter stated, has no effect on WOT performance. So using a stock PROM and a plugged EGR, combustion temps increase under normal driving condition because of a lean condition, and pinging starts. This happens because the EGR is adding exhaust air (doesn't burn well) that has the net effect of shrinking the combustion chamber. When pining starts, the ECM cuts back timing. Using a scanner, I could watch this happen. Engine performance and MPG drop when the ECM retards timing. The 1989 and 1990 L98 use the most agressive timing curves of all the L98s. This was possible because GM changed injector design that atomized the fuel better. How did I learn all of this? My EGR was not working properly all of the time. I plugged in a scanner and manually controlled the EGR using a vacuum pump. Driving at 40 MPH, I could force pinging by closing the EGR (no vacuum), and watch the ECM retard timing. If I open the EGR (added vacuum), it didn't take more that one mile of driving for the pinging to stop and timing went back up. Side comment that I didn't have time to test. It appeared like engine temp on my digital dash was higher with the EGR not working. I suspect this was caused by the higher head temps and retarded timing. Hope this helps.

 

[ZumZum]

If you block off the EGR you definitely need to get your chip reprogrammed to eliminate the EGR function.

I think the L98 has a bad EGR design. It seems counter-intuitive to allow exhaust gases after they immediately exit the combustion chamber to re-enter the chamber to "reduce combustion temps".

 

[bucket]

i dont know of a street leagle chip for my 92 that eliminates all the smog, i did have one made at hypertech for a pickup i had that eliminated everything and advanced the spark etc...i told them(hypertech) i was building a mud bog racer...lol
but way out west we have to pass a smog test so...mods are limited and, to be frank, almost usless in this traffic....
logic tells me to just turn the key and drive...but something in my brain( dain brammage?) tells me it could be better....lol

 

[bucket]

yes thats a good answer and one i can live with...thanx

 

[zerokool2]

Hi I have 1990 and I recently changed my injectors soon after started getting a code 32 when driving at about 65mph for about 10 miles or so not sure if this problem is related to the injectors but could use some help getting to the bottom of this Thanks!

 

[Schrade]

Hi I have 1990 and I recently changed my injectors soon after started getting a code 32 when driving at about 65mph for about 10 miles or so not sure if this problem is related to the injectors but could use some help getting to the bottom of this Thanks!

Good job using the search function! Most folks just create a new thread, and kinda clutter up the forums.

The ECM purges the gas tank fuel vapors from the EVAP cannister. It cycles every 10 - 12 minutes at speed (not sure what 'spec' time is tho'). The EGR solenoid redirects vacuum to the cannister to draw the vapors.

After 15 seconds or so, the computer looks to see if the vacuum holds. If there's a hole in the cannister, or if there's a hole in the vacuum hose, then vacuum won't hold, and the computer reads a vacuum leak. If the EVAP 'reservoir' includes the vapor line all the way from the gas tank, THEN a faulty gas cap could even cause vacuum to not hold, and same result - ECM says Problem, and lights the 32 code.

 

[Schrade]

I don't know L98 test for EVAP integrity, so here's one way to diagnose (besides using a hand vacuum pump):

Find the hose that goes TO the EVAP cannister FROM the intake. Pull it and plug it at the cannister. Drive, FULLY warmed up, at speed for 15+ minutes. No light means the cannister gets the rap. If it lights anyway, the hose has a hole, or the solenoid switch is faulty, which was supposed to close the vacuum to the EVAP.

If you get that far, post back...

 

[redvett]

Gas tank evap was not monitored until OBD2 in 1996. Gas tank fuel vapors are collected in the canister until you start driving and then the PCM allows the vapors to be burnt instead of going to the atmosphere saving your gas & money.

 

[zerokool2]

Hi I have 1990 and I recently changed my injectors soon after started getting a code 32 when driving at about 65mph for about 10 miles or so not sure if this problem is related to the injectors but could use some help getting to the bottom of this Thanks!

Update!! I disconnected the vacuum line going to the egr valve and connected a mighty vac to it and it made no difference at idle also it didnt seem to hold any sort of vacuum at all, thoughts anyone?? Im guessing the egr valve went bad.

 

[Schrade]

To test the EGR valve itself, stick your finger through the little brackets in the valve, and press on the diaphragm. The engine will stumble.

If it's stumbling or loping already, the pintle valve that's connected to the diaphragm could be stuck open from carbon fouling, which creates a vacuum leak.

 

[zerokool2]

Im not sure what you mean by little brackets on the egr ?it looks like a round sealed unit with two bolts that hold it down to the intake unless you meant for me to take it off and then look inside but that looks like I will have to remove tha plenum to get it out

 

[Schrade]

There's a couple of brackets, kind of like the backside of a car speaker. See pic, right speaker. Press the diaphragm between the brackets, to pull the pintle downward.

You don't have to remove it to test...

 

[gw962]

The 90 uses a positive pressure EGR. Check this link for info on how to test.
http://www.tomco-inc.com/Tech_Tips/ttt26.pdf

 

[JAKE]

The 90 uses a positive pressure EGR. Check this link for info on how to test.
http://www.tomco-inc.com/Tech_Tips/ttt26.pdf

What's an easy way to tell which type I have? My car's a 96.

Thanks,

Jake

West Point ROCKS!

 

[gw962]

Jake, I don't know much about the LT engine setup, but I'm sure the EGR is easier to access than the L98. I would think that either P or N would be the last letter stamped on the housing, but that is just a guess. Sorry.